Williams, the top seed and defending champion, fired seven aces en route to a 62-minute, 62 61 victory, her 25th victory in her last 26 matches.

"I definitely felt a little sluggish today, but it was fine, and it was good to get that win," Williams said in her presser. "I'll feel better after having tomorrow off and more time to get adjusted. I'm still waking up at like two in the morning.

"It's really bright out there too - I was so used to all the gloom in London and all the clouds - but other than that the weather was just great here today."

The 19-year-old Gibbs, who is the reigning NCAA champion in both singles and doubles, idolized Williams as a kid and was even a ballgirl for her at age 12.

"I think she played really well - she moves really well and she doesn't quit, and I think that's the best quality you can have as an athlete, and especially as a tennis player. She could have easily given up and she didn't. She's a fighter. And she has a really good first serve. I think she really held her own today.

"When I played Monica Seles for the first time it was pretty cool. To think someone would still want to be like me is kind of awesome."

Gibbs was in her first WTA main draw, and had won her first round match against Noppawan Lertcheewakarn before facing Williams second round.

"It was a great experience - it was really good to match up against that level and see what's out there," Gibbs said. "She's such a hero in my mind and so built up in my mind, but I think I was definitely more in the match than I had anticipated being. After a few points I felt I could at least compete at that level."

"Serena will definitely be a challenge, but I'm ready to go out and just enjoy it," said Scheepers, who is now in her first Premier-level quarterfinal. "I'm happy with how the hardcourt season has started and I hope to keep this up."

"I'm definitely a lot more consistent off the ground than when I played her a few years ago, and her pace isn't as intimidating as it was when I was a little bit slower," Vandeweghe said. "Having the confidence I can put more balls in the court helps me prepare against someone who moves as well as she does.

"I also had to keep going for my shots today, which I think I did pretty well."

Vandeweghe's win over the World No.20 was her third career Top 20 win, having beaten Vera Zvonareva and Aravane Rezai during the 2010 season.

"I've had a bit of a good run as of late, making the finals of Nottingham on grass and qualifying for Wimbledon, so I'm playing well," Vandeweghe said. "I think I'm putting some good matches together and having the confidence of being able to close out some of these close matches really does help on the court.

"Jan-Michael and I have been working hard, drilling a lot - he's really on me. He's not here this week, he's playing World Team Tennis, but my mom's here."

Defending champion Angelique Kerber and the returning Serena Williams headline the acceptance list for the 2017 Australian Open. Meanwhile, Australian teenager Lizette Cabrera and Luksika Kumkhum have earned the first two wildcards.